This invention relates generally to vehicle air bag installations and, more particularly, to a device for controlling deployment of an air bag.
Inflatable occupant restraint systems for passengers of vehicles conventionally comprise an air bag assembly having an inflatable air bag, an inflator and a container for housing the inflator and the air bag. The air bag is folded atop the inflator beneath the open top of the container. This assembly is mounted in a recess in the instrument panel for deployment of the air bag through a deployment opening in the instrument panel. This opening is closed by a cover door.
The instrument panel opening can be located in the front face of the instrument panel or in the upper surface of the panel. Positioning of this opening in the front face of the instrument panel complicates location of the glove box. Consequently, it is more convenient to locate this opening in the upper surface of the instrument panel.
In some vehicles the air bag cover door comprises a foam pad and skin which are an integral portion of the panel. A supporting substrate is cut out to define the door shape. Upon deployment, the inflating air bag forces a door-shaped cutter to rip through the panel foam and skin to release the inflating air bag.
In other vehicles the skin includes a tear seam line of weakened panel material along the substrate cutout on three sides to define the door. This tear seam is fractured by the inflating air bag so that the door swings open about its fourth side, which functions as a hinge, to enable the air bag to properly deploy.
In yet other vehicles this cover door is a separate rectangular panel that is flush mounted in a rectangular opening in the surrounding panel area so that it can be opened and completely removed by the deploying air bag upon inflation. This type of door is usually attached to the instrument panel at its forward edge by a hinge or by a tethering device to cause the door to swing open about this attachment out of the path of the deploying air bag.
It is essential that this type of door be releasably installed in the panel opening so that it completely separates and moves out of the way of the deploying air bag. However, the door must remain attached to the instrument panel upon opening so that it does not become a hazard to occupant safety.
Upon actuation of the inflator, the air bag begins inflating and exerts an increasing force on the cover door, bursting it open with considerable force. The bag then unfolds and inflates in a manner partially determined by how the bag was originally folded, by the location of the instrument panel deployment opening, and by the location of the cover door when open.
With the opening located in the upper surface of the instrument panel, the inflating air bag must deploy initially upwardly and must then deploy rearwardly. Many different methods of folding the air bag have been devised to tailor air bag deployment to a particular vehicle environment. Also, devices have been developed which locate the cover door in a desired position when opened. One of these includes front and side tethers which locate the cover door in a position spaced above the instrument panel and spaced from the windshield. These tethers and the door create a chute which directs deployment of the inflating air bag from the initial vertical movement to rearward movement. These tethers must be quite strong to resist the force exerted continuously by the inflating air bag.
The inflator is first mounted in the container and the air bag is attached and hand folded into the container to form the air bag assembly. Since the air bag assembly is normally transported and handled several times prior to installation in a vehicle, a protective cover is then attached over the container opening to cover the air bag. Since the air bag must deploy through this cover, it must be sufficiently flimsy to be easily burst open by the inflating air bag.
It would be desirable to provide an air bag assembly which provides a deployment chute to direct air bag deployment rearward that does not require that the cover door have side tethers.
It would also be desirable to provide an air bag assembly which does not require the cover door and its tethers to bear the continual force exerted by the deploying air bag.
It would be further desirable to provide an air bag assembly which includes a rigid air bag cover to protect the air bag during pre-installation handling.